High power transistors frequently occupy a major portion of the chip area in a high power integrated circuit. Vertical high power devices occupy much less area than horizontal high power devices but require contacts to carry current from the buried drain or buried collector. Typically a sinker contact is formed by implanting dopant at a series of different energies to form a highly doped diffusion column from the surface of the substrate down to the buried drain or buried collector. Even with the sinker contact diffusion when high current flows through the diffusion a significant voltage drop may occur limiting the performance of the vertical high power transistors.
Some devices in integrated circuits require low contact resistance for improved performance. Typically to reduce contact resistance the diffusion area is increased and multiple contacts are formed to the diffusion. This increases area of the integrated circuit and may also increase diffusion capacitance which may reduce circuit performance.